Attenuation Correction factor and PET/CT artefacts in Head & Neck cancers. By Biprojit Nath M.Sc. Nuclear Medicine IIT Kharagpur & Tata Medical Center, Kolkata What is Attenuation Correction? μ= linear attenuation coefficient of the tissue at 511KeV Pdet Is independent on source location along the line joining two detectors. Attenuation correction for PET • Transmission scanning with an external 511 keV photon source (Ge-68) can be used for estimation of attenuation in the emission scan. • The fraction absorbed in a transmission scan, along the same line of response (LOR) can be used to correct the emission scan data. • The transmission scan can also be used to form an attenuation image. • Attenuation Correction factor for a detector(i,j) pair: How can we use the CT data for CT-based attenuation correction (CTAC)? Comparing X-ray and PET • CT Attenuation only, but with complicated energy weighting of source intensity and material-specific absorption • PET
